DNA methylation-induced suppression of PRDM16 in colorectal cancer metastasis through the PPARγ/EMT pathway.

Background: PR/SET domain 16 (PRDM16) is an important transcription factor in the differentiation process of brown adipocytes, which plays an important role in maintaining the special morphological characteristics and cellular function of brown adipocytes. However, the role of PRDM16 in human colorectal cancer (CRC) is currently unknown.

Methods: Methylation sequencing, methylation-specific PCR (MSP), multiple bioinformatics analyses, Co-Immunoprecipitation (Co-IP) assay and Immunofluorescence (IF) staining, in vitro and in vivo functional experiments were performed to study the biological role of PRDM16 in CRC progression.

Results: Our study found that methylation level of PRDM16 was associated with CRC and lung metastasis of CRC by DNA methylation sequencing. Furthermore, we identified methylation sites within the promoter region of PRDM16. PRDM16 expression was significantly lower in human CRC tissue samples and dramatically associated with tumor size, T stage, overall survival rates and disease-free survival rates of CRC patients. Down-regulation of PRDM16 significantly promoted proliferation, migration, and invasion of CRC cells by regulating EMT pathway in vitro and in vivo. Decitabine which was a methylate inhibitor increased PRDM16 expression and inhibited CRC progression in vitro and in vivo. Further study showed that PRDM16 interacted with PPAR γ in nucleus and upregulated its expression in CRC. PPAR γ expression was lower in CRC tissues compared with the adjacent colorectal mucosal tissues. PPAR γ suppressed CRC progression including proliferation, colony formation, migration and invasion via EMT pathway, but not affect PRDM16 expression. Decitabine treatment could reverse the biological effects caused by PPAR γ down-regulation in CRC cells.

Conclusion: Our study first shows that DNA methylation-mediated suppresser role of PRDM16 in CRC progression via PPAR γ/EMT pathway.